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UniTn STATES aTnT Tricia,

ROBERT J. TILFORD AND HENRY MY. REDEMANN, OF LOUISVILL l, KEN'lllCKY,

ASSIGNORS TO THE REDEMANN- PLACE.

TILFORD STEEL COMPANY, OF SAME MANUFACTURE OF STEEL.

SPECIFICATION forming part of Letters Patent No. 897,476, dated February5, 188 9.

Application filed July 25, 1888.

To all whom it may concern:

Be it known that we, Roenn'r J. TILFORD and HFNRY M. REDEMANN, citizensof the United States, residing at Iamisville, Kentucky, have inventednew and useful Improvements in the Process of. Hardening S1 eel, ofwhich the :t'ollowing' is a specification.

()ur invention relates to certain new and useful improvements in thetreatment of crude or low-grade steel to produce a refined or high-gradesteel.

The most successful method of producing low-grade steel that known asthe Bessemer process, described in his patent of 1855; but this product,as is well known,is suitable chiefly for railways, axles, and like uses,and is totally unsuited for structures, machinery, and tool purposesunless 'repuddlcd, hammered, and rolled, tor the reason that in itsnormal state it is too soft, and when hardened itbecomcs too hard andbrittletm' thepur- It was the recognition of these i nherent dcl'ccts inthe Bessemer and low and medium grade steel which led ustotheinvcstication of the subject which has developed our presentinvention, the object oi which is the production at slight cost and aminimum degree of labm'ot' t igher grz-tde and more rcfined steel bytrcatin 5,1" the Bessemer and other low-grade steel in such manner as toproduce a molecular change from a coarse grain to a .tine grain andsilky fracture, to increase the tensile strength, elasticity, toughness,and ductility, and to greatly increase the carbon. \Ve have found fromexperience that uniform results in all instances flow from the trcatment of metals having like properties.

\Vith these ends in view our invention con sists in heatin low-gradesteel to a degree of heat re ilrcscntml by white heat, and thensubjecting' the metal so heated to a previouslypreparcd liquid bath ofsuch character that the contzict ot' the lunttwl metal and liquid bathwill gmierate hydrocarlmn gases, which will be a'bsliirbcd or taken upby the metal, and allowing, the metal to remain in the bath until it hasbecome substantially cool, in contradistinction to what is known as thecementation or dry process, as will be hereinafter more fully set forth.

Serial No. 231,018. (Specimens) As an illustration of one of the bathsemployed in the practice of our invention, we would state that we employglycerinc andwater in the proportion otf th ree ounces of glye crinetioone-half (1}) gallon ot water, and all0w---55 the' change is ellectel'l,which should be until the metal substantially cool, or until suchreduction in heat in the metal is made that it will no longer take upthe gases generated by contact with the bath. \\'e have also found thatby addin to the bath of glycerine and water spirits of .niter,aqua-ammonia, chloride of ammonium, sulphate of zinc, sulphate ofalumina, and ammonia the results and effects obtained by a bath of'cerine and water alone are improved, althou h good results areoliitaincd by the latter.

In practicing" our invention by the last named bath we employ theseveral chemical bodies in about the .t'ollowin proportions, to wit:spirits of niter,onc and ahalt' (l ounce; aqna-ammonia, one and a half(14-) ounce; chloride of annnonium, two ounces; sulphate of zinc, oneand a halt (111,) ounce; sulphate ot alumina and ammonia, one and a half(1%) ounce; glyccrinc, three (53) ounces; water, one-halt gallon.

\Ve desire to state herein, however, that we lay no specific claim toeitherof the baths 8o dcscri bed above by which we practice our invention, as the one first described forms the subject-matter of a divisionalapplication of this case filed on 13th day of November, 1888, Serial No.990,737, while the second bath described forms the subject-matter of asecond divisional application filed on the same day and bearing SerialNo. 200,738, to which divisional applications reference is made for amore full. and complete description of the manner of carrying out thegeneric idea which the present application is intended to cover.

As further explanatory, however, of the advantages gained by the presentinvention, we would state that by the practice of our proccss (whichshould be understood as being distinguished from processes for temperingsteel in oil) the nature, the physical construction, and the molecularconstruction of the metal are completely changed, whereas the the heatedmetal to remain submerged until tempering of steel in oil, as practicedby some processes, simply tempers the steel more slowly than is done bytempering in water and other properties, leaving the metal less hard,but som ewhat tougher than water-tempered matcrial. The changes causedby the oil-tempering process are merely temporary, and do not change thephysical or granular construction of the metal, and such changes as arecaused thereby can be readily neutralized by reheatin and allowing themetal to cool. The changes caused by treatment by our process arepermanent, and cannot be removed by any known treatment or processwithout entirely destroying the steel properties of the metal byl'nu'ning.

\Ve have of course been unable to analyze the gases resulting from thecontact of the hot-metal body with the bath, but are led to believe thatthey constitute a hydrocarbon gas which has a strong allinity for themetal, and that the. latter, being in a heated state, is in such aphysical condition as to readily take up or absorb such gas; but as tothe fact that the metal is highly improved we have no doubt whatever, ashas been demonstrated by all the well-known scientific and m(-cht1niealtests.

It will be understood, of course, that when the treatment is appliedadjacent to the furnaces where the low-grade steel is manufactured. theingots may be treated without reheating, and thus the expense of suchreheating is avoid ed. After the metal has been subjected to thetreatment it is allowed to cool in the ordinary manner, and it mayatterwanl be subjected to any culinary hardening or tempering process,and the temper may, if necessary, be drawn and again restored without atall atli'ecting the other properties acquired from the bath.

\\e are of course aware that the quality of Bessemer and other low andmedium grade steel may be improved by what is known as the dry orcementation process, which requires a large expenditure of skilled laborand great length of time, and that, too, without always securing uniformand satisfactory results.

*0 desire itto be distinctly understood that we lay no claim to thebroad idea of in.- creasing the quality of steel by subsequenttreatment, as that has been heretofore done, especially by what is knownas the cementation process, which may be termed a dry process, ourinvention differing from such process in the particular that it requiresa period of time amounting to a small percentage of the time required inthe cementation or dry process, and is in eol'itradistinction to suchprocess essentially a liquid or wet process, the former requiring manydays, while the latter involves only a few minutes.

By our invention we greatly increase the tensile strength andelasticity, and yet do not destroy the per cent. of reduction orductility, while with ordinary tempering the tensile strength andelasticity are greatly increased, but the per eent. of reduction andductility is very much impaired.

Having thus described our invention, what we claim as new, and desire tosecure by Lettei s Patent, is

The process of converting low-grade steel into refined or high-gradesteel, which consists in first heating the metal to be treated to adegree of heatrepresented by white heat,

